Permanent magnet synchronous motor including permanent magnet with tapered outer edges and rotor core with opening

Abstract

The present invention provides a permanent-magnet-synchronous-motor having a stator with concentrated windings with the following structure so that permanent magnet ( 6 ) is hard to subjected to demagnetization magnetic field: 0.3 Lg<La≦2.0 Lg, where La is a clearance between teeth of stator ( 1 ), and Lg is an air-gap between stator ( 1 ) and rotor ( 2 ). Outer walls of both ends of the permanent magnet ( 6 ) disposed within rotor ( 2 ) in a rim direction may be tapered toward inside from a rotor rim in a radial direction and to form a recessed section on the outer walls of the magnets. As a result, withstanding force against demagnetization is expected to increase.

1. A permanent magnet synchronous motor comprising:
 a rotor including:
 a rotor core; 
 a reversely-arced permanent magnet buried in said rotor core such that an end of said permanent magnet faces an outer wall of said rotor core, said rotor core having an opening between said end of said permanent magnet and said outer wall of said rotor core for preventing demagnetization of said permanent magnet; and 
 
 a stator including teeth and concentrated windings such that adjacent teeth have different polarities; 
 wherein said rotor and said stator are arranged to satisfy the relationships: 
 Lg<Q<3 Lg; and 
 0.10 As<Am<0.25 As, wherein:
 Lg is a size of an air gap between said rotor and said stator; 
 Q is a distance between said end of said permanent magnet and said outer wall of said rotor core; 
 Am is an angle of an arc length of said end of said permanent magnet measured with respect to a central axis of said rotor; and 
 As is an angle of an arc length of each tooth of said stator measured with respect to said central axis of said rotor. 
 
 
   
   
     2. The motor of  claim 1  wherein said permanent magnet comprises a ferrite permanent magnet. 
   
   
     3. The motor of  claim 1  wherein said stator has a divided core. 
   
   
     4. The motor of  claim 1  wherein said rotor and said stator are adapted to operate sensor-free. 
   
   
     5. The motor of  claim 1  wherein said permanent magnet comprises one of a plurality of reversely-arced permanent magnets evenly spaced within said rotor core, each of said permanent magnets being arranged such that each end of each of said permanent magnets faces said outer wall of said rotor core. 
   
   
     6. An apparatus comprising:
 a compressor in one of an air-conditioner and an electric refrigerator; and 
 a permanent magnet synchronous motor for driving said compressor, said motor comprising:
 a rotor including:
 a rotor core; 
 a reversely-arced permanent magnet buried in said rotor core such that an end of said permanent magnet faces an outer wall of said rotor core, said rotor core having an opening between said end of said permanent magnet and said outer wall of said rotor core for preventing demagnetization of said permanent magnet; and 
 
 a stator including teeth and concentrated windings such that adjacent teeth have different polarities; 
 wherein said rotor and said stator are arranged to satisfy the relationships: 
 Lg<Q<3 Lg; and 
 0.10 As<Am<0.25 As, wherein:
 Lg is a size of an air gap between said rotor and said stator; 
 Q is a distance between said end of said permanent magnet and said outer wall of said rotor core; 
 Am is an angle of an arc length of said end of said permanent magnet measured with respect to a central axis of said rotor; and 
 As is an angle of an arc length of each tooth of said stator measured with respect to said central axis of said rotor. 
 
 
 
   
   
     7. The apparatus of  claim 6 , wherein said permanent magnet comprises a ferrite permanent magnet. 
   
   
     8. The apparatus of  claim 6  wherein said stator has a divided core. 
   
   
     9. The apparatus of  claim 6  wherein said rotor and said stator are adapted to operate sensor-free. 
   
   
     10. The apparatus of  claim 6  wherein said permanent magnet comprises one of a plurality of reversely-arced permanent magnets evenly spaced within said rotor core, each of said permanent magnets being arranged such that each end of each of said permanent magnets faces said outer wall of said rotor core.